A model for giant magnetostrain and magnetization in the martensitic phase of NiMnGa alloys

A model on the basis of transformation kinetics is developed in this paper in which magnetic-field-induced stress is introduced and the equivalence principle is employed for mechanical and magnetoelastic deformation. An exponential expression is given to describe the field dependence of magnetization for martensitic variants. A good agreement between the theoretical calculations and the experimental results is achieved for the non-stoichiometric Ni₂MnGa alloys. The proposed simple model is acceptable for describing magnetization and magnetic-field-induced strain behavior of ferromagnetic shape memory NiMnGa alloys.